The present invention relates to hydraulic systems generally and more particularly to an improved flow control valve and a hydraulic actuator system employing the valve.
The present invention is an improvement on the valves and systems disclosed in my earlier patents, e.g. U.S. Pat. Nos. 4,696,163 and 4,766,728. Both of those patents relate to flow matching valves and bidirectional actuator systems employing the valves. The particular systems disclosed in those patents employed stepper motors to operate a bidirectional hydraulic gear pump. The pumps were necessarily finished to very close tolerances in order to have low leakage. While these prior art systems provided for very precise control of a hydraulic actuator or piston, cost was relatively high due both to the cost of the stepper motors employed and the electronic driver circuitry necessitated by the use of those motors.
Among the several objects of the present invention may be noted the provision of a hydraulic actuator system which can utilize more common a.c. and d.c. motors; the provision of such a system in which the motor is not loaded when no movement is required of the actuator; the provision of such a system in which the hydraulic operation will act as a brake on the motor; the provision of such a system which does not require exceptionally low leakage pumps to drive the system; the provision of such a system which will provide highly precise control of an actuator; the provision of such a system which will provide for bidirectional operation of an actuator; the provision of such a system which is highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.